The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
As operators demand the flattening of broadband networks (i.e., reducing network layers) to save cost, DSLAM performs more functions that used to be performed by layer 2 and layer 3 switches or routers, such as upper-layer protocol packet processing and IP forwarding. Since a large amount of the protocol packets need to be analyzed by software modules in the DSLAM, the load of the CPU in the DSLAM is usually high. The occupancy rate of the CPU may reach even 100% if there are too many protocol packets to be processed, which makes it impossible to process other important processes in time and even starves these processes. The consequence brought about by the heavy load of the CPU is unpredictable and may be extremely serious like resetting of the whole DSLAM.
In the related art there are two protection methods to ensure the safe operation of a DSLAM and protect the DSLAM from the impact of various illegal packets.
In the first method, the number of subscribers accessing to the DSLAM is limited through binding a static Multimedia Access Control (MAC) address to each XDSL port or setting a maximum MAC address learning number for each XDSL port, so as to prevent simultaneous accesses or attacks from multiple terminals on the subscriber side, and thereby protecting the DSLAM.
In the second method, in order to protect the DSLAM from the attack of a single subscriber who sends large amounts of protocol packets to the DSLAM with a packet-sending tool, the software module of the DSLAM analyzes the traffic amount of the protocol packets (regardless of the type of the protocol packets) that need to be processed during a time unit, limits the traffic amount of the protocol packets to be processed per second and directly discards the excessive protocol packets (regardless of the type of the protocol packets).
The attacking packets currently on the network are usually initiated from the subscriber side, i.e., the XDSL access side, where illegal subscribers send large amounts of packets to upper layer networks with packet-sending tools. The DSLAM mainly processes Address Resolution Protocol (ARP) packets, Internet Group Management Protocol (IGMP) packets, PPP over Ethernet (PPPOE) packets and Dynamic Host Configuration Protocol (DHCP) packets, if the subscriber side sends large amounts of these packets to the DSLAM and the DSLAM has to process all of these packets from the subscriber side, the load of the CPU in the DSLAM will be very heavy and may put the DSLAM at the risk of reset.